Treatment Of Black And Odorous Water By Biological Carbon-based Immobilized Microorganisms

The problem of black-odor water not only influences the city landscape but also directly affects the quality of people’s daily lives.The Action Plan for Prevention and Control of Water Pollution enacted in 2015 proposes to eliminate black-odor water bodies.At present,the treatments for black-odor water have three categories according to the technologies:physical,chemical,and biological methods.And the biological method is the most economic and efficient treatment for the ecosystem of rivers in a long run.Therefore,this thesis analyzes the performance of the self-made biochar-immobilized microbes in treating black-odor water.The thesis first describes the method of using walnut shells with the high-temperature pyrolysis method to produce biochar,whose production requirements are optimized by the Response Surface Methodology.Then,the bacteria strains with degradation function were selected from the sediments of black-odor water,and immobilized on the modified walnut shell by adsorption method and embedding method respectively.Finally,this thesis examines the effectiveness and mechanism of the modified biochar（immobilized body）treatment for the common pollutants NH₄⁺-N,COD,and TP in black-odor water.Through the response surface methodology,the optimal preparation conditions of the modified walnut shell biochar were obtained as follows:the pyrolysis time was 2 h;the preparation temperature was 700℃;the concentration of nitric acid was 5.5 mol/L;and the equilibrium adsorption capacities for NH₄⁺-N and COD were respectively 3.83 mg/g and 8.12mg/g.The adsorption of NH₄⁺-N by modified biochar is a pseudo-first-order kinetic equation,and the adsorption of COD is a pseudo-second-order kinetic equation;the isothermal adsorption model of the two is the Langmuir model.Through SEM,FTIR,XRD and other testings,and analyzing the physicochemical properties of modified walnut shell biochar,it was found that the modified walnut shell biochar had stable surface structure and good pore structure,which could provide good living condition for microbes,and has a certain degree of reusability.After 16S r DNA sequencing analysis,the strain N3 immobilized on the modified biochar was Bacillus subtilis subsp.Under the conditions of p H=7,temperature of 35℃,and dosage of 1m L/100m L,within 3d,the degradation rates of NH₄⁺-N,COD and TP reached 71.24%,74.26%and 31.43%,respectively.Through SEM,FTIR,XRD and other detection methods,the immobilized microorganisms（XF-K）prepared by the adsorption method were more abundant in functional groups than the immobilized microorganisms（BM-K）prepared by the embedding method,and the surface structure was more conducive to the growth of microorganisms.Under the conditions of p H 7,temperature 35°C,and dosage of 1g/100m L,the degradation rates of NH₄⁺-N,COD and TP in simulated black and odorous water by XF-K within 3 days were 85.35%,92.12%and 53.82%,and XF-K has certain reusability.The degradation of NH₄⁺-N,COD and TP by XF-K conforms to pseudo-second-order kinetics,and internal diffusion is not the main controlling step in the degradation process;the L-type model can better describe the adsorption of NH₄⁺-N by XF-K,the F-type model can better describe the adsorption of TP;the degradation process of XF-K to pollutants can be roughly divided into two steps:the first step is mainly the adsorption of biochar,and the second step is mainly the degradation of microorganisms,and both functions exist simultaneously.Under the external natural conditions,the degradation rates of NH₄⁺-N,COD and TP in actual black and odorous water by strain N3 were 48.18%,41.56%and 11.45%,respectively,while the degradation rates of NH₄⁺-N,COD and TP in actual black and odorous water by XK-F The degradation rates were 78.15%,74.51%and 31.77%respectively,and the COD concentration decreased from 112.31mg/L to 28.62mg/L,which reached the standard of Class IV water.By comparison,it was found that the immobilized microorganisms had better degradation effect on pollutants.